Irradiated tobacco process and product



United States Patent 3,472,237 IRRADIATED TOBACCO PROCESS AND PRODUCT John T. Stephens, Brooksville, Fla., assignor to Steber Corporation, Washington, DC. No Drawing. Filed May 24, 1967, Ser. No. 640,824 Int. Cl. A24b /00, 9/00 U.S. Cl. 131-121 10 Claims ABSTRACT OF THE DISCLOSURE The present invention comprises a process and resulting product for treating tobacco pretreated to substantially decrease the moisture content by contact with a drying medium whose moisture content is below which comprises impregnating the tobacco with about 0.5 to 8.0% by weight of the dry tobacco of a metal oxide impregnant selected from the group consisting of iron, calcium and copper oxides, and mixtures of and hydrates thereof, at least one-third of such metal oxides being iron oxide and the metal oxide being disposed in the form of a dispersion with an active carrier selected from the group consisting of reducing sugars and carbohydrates hydrolyzable to reducing sugars.

The impregnated tobacco is selectively irradiated with an efiective amount of visible light in the ranges 4000- 5000 A. and 60004000 A., and ultra-violet light below 3400 A. to form a chemical combination of the metal oxide, sugar carrier and the tobacco fibers. The tobacco is then dried to eliminate Water and the tobacco is separated, vacuum cleaned and processed. Later, during the burning process when the tobacco is utilized for smoking, the catalytic metal oxides chemically bound to the tobacco fibers by the irradiation treatment, drastically reduce the amount of carbon monoxide available to the smoker.

The field of invention lies within the general area of modification of tobacco so that by some means, here catalytically, there is a modification or change in the character of the volatile components of the tobacco which are released during the smoking process. The present application alleges a significant and sharp reduction in the amount of carbon monoxide available to the smoker using tobacco which has been treated by the process.

U.S. Patent 2,003,690 of Lewton incorporates finely divided ferric or ferrous/ferric oxides in tobacco fibers but fails to disclose an effective method of retaining the additive within the tobacco fibers to obtain an efficient product and eliminate troublesome staining from the oxide content.

U.S. Patent 2,007,407 to Sadtler adds colloidal silica gel, colloidal alumina hydroxide, aluminum oxide or titanium oxide to tobacco fibers for purposes of masking a bitter taste.

Canadian Patent 680,761 to Parmele (Lorillard Co.) 1964, and the related British Patents 863,287 (1961) and 903,067 (1962) all to Lorillard Co., based on a United States application of Dec. 13, 1957, utilize as catalysts oxides of magnesium, iron, calcium and copper which may be admixed with the tobacco in a glucose solution or as a slurry suspension.

None of these patents in the prior art teaches the critical features of this invention of relative fixing the additive within the tobacco fibers by means of chemical combination induced by excitation of irradiation in specially selected light bands.

An additional feature of this invention not considered in the prior art, is the pretreatment of the tobacco prior to impregnation, which comprises reducing the moisture content by contact with dry air of below 20% moisture 3,472,237 Patented Oct. 14, 1969 content enabling a greater amount of catalytic additive to be placed in the tobacco for action later upon smoking.

In the past decade much attention has been given to the carcinogenic properties of components of tobacco smoke, such as tars and phenols. Until 1966, very little attention was placed upon a tobacco or cigarette which during the smoking process would deliver a sharply reduced amount of carbon monoxide (CO) to the lungs. In 1966 Otto Warburg, twice winner of the Nobel Prize and Director of the Max Plank Institute, Berlin, Germany, speaking at the 1966 Annual Meeting of Nobelists at Lindau, Germany, published his now famous paper entitled Primary and Secondary Causes of Cancer. Briefly, the Warburg thesis is that the prime cause of cancer is the replacement of the respiration of oxygen in normal body cells by fermentation of sugar, or in other words, that cancer may be caused primarily by a deprivation of oxygen. It is well known that hemoglobin will preferentially chemically absorb carbon monoxide and oxygen in a ratio of about 300 to 1. Naturally, the attention of present day investigators shifted to consideration of means. for reducing the amount of carbon monoxide produced in substantial quantities during the smoking process, and attention was directed towards alteration of the CO- molecule so that this factor would be eliminated from consideration in smoke produced in the smoking process. The prior art above has indicated that the catalytic metal oxides for altering carbon monoxide to carbon dioxide are well known.

THE METAL OXIDE CATALYST The principal function of the metal oxide catalyst during the present process is to catalyze the oxidation of the carbon monoxide produced in combustion in the smoking process to carbon dioxide.

It has been found that, at the combustion temperature, the smoke products form in the cigarette at a temperature of about 850 to 900 C. At this temperature metal oxides, such as iron, calcium and copper, are reduced to the metallic state and there effectively catalyze the reaction of the oxidation of the CO- CO In order to also catalyze the Hill reaction between sugar precursors by photosynthesis, it is necessary that at least about one-third of the metal oxide be present in the form of ferric oxide hydrated to make available a source of ferric ions at the impregnated tobacco sites.

By means of the irradiation process, the adsorption of the metal oxide in the fibers of the tobacco can be made permanent by chemical combination. Additionally, the predrying of the tobacco at a relatively low humidity to lower the moisture content to a minimum insures that up to 10% of metal oxide by weight of the dry tobacco fibers can be impregnated thereon.

Depending upon the burning rate of tobacco governing the rate and amount of carbon monoxide produced in the smoking process, the taste, appearance and other variables to the operable range of weight percent of metal oxide additive will be between 0.5 and 10%.

THE SUGAR CARRIE-R Operable sugar carriers in the present reaction include most monoand disaccharides. Preferred sugars are the so-called reducing sugars such as hydrolyzed sucrose providing invert sugar (D-fructose). Such reducing sugars indicate the presence of the aldehyde group which is preferable in the later use of the carrier. In addition to sucrose, the following sugars are exemplary: maltose, lactose, glucose, mannose, etc. The sugars are selected as carriers to fulfill an active role later in the irradiation step. It is postulated that under the irradiation bombardment, the energy levels of the keto and aldehyde groups in the sugars act to form complexes with the metal oxide as do the similarly excitated cellulose fibers containing cellulose reactive groups.

While wide variation may be practiced in the ratio of metal oxide to sugar carrier, a preferred ratio is about 1 part metal oxide to 4 parts sugar carrier. An important mixing and hydrolysis step in the present process is the necessary agitation and heating of the oxide-sugar dispersion after admixture and water addition. This period of heating at the boiling point is carried out from 5 to 30 minutes with vigorous agitation. This pretreatment serves to disperse the oxide in the carrier for purposes of homogeneity and also serves to hydrolyze at least in part the metal oxide containing ferric oxide so that a substantial proportion of hydrated ferric oxide is present to provide Fe+3 ions for the Hill reaction (R. Hill, Nature Magazine, vol. 139, p. 881) (1937). The Hill reaction provides that in the presence of ferric ion and water the chloroplasts (chlorophyll) in the tobacco fibers will act enzymatically under irradiation to produce active hydrogen and oxygen. Carried further, formaldehyde may also be produced, and U8. Patent 2,121,881, Prudhomme, teaches the formation of the hexoses from formaldehyde by conventional irradiation with orange-colored light bulbs.

A preferred ratio of sugar carrier to metal oxide is 4:1 and an operable range is 1:1 to :1 by weight. The mix is then added to water in a preferred amount of about 250 grams of the sugar oxide mix to 1 liter of water. A range of 50 grams per liter to 1500 grams per liter is operable.

IMPREGNATION OF THE TOBACCO FIBERS Tobacco fibers are desorbed by such conventional treatment as heating circulating dry air until equilibrium conditions are reached using as treating medium dry air whose moisture content is below 20%. Parups and Hoffman indicate (Tobacco Science, May 15, 1964, pp. 4548, vol. 158, No. 20) that in most cases the differential between moisture desired and moisture available in tobacco can be achieved in 6 to 8 hours when the moisture curve reaches a plateau. The predried tobacco fibers are now immersed in the impregnating medium while the latter is stirred or otherwise agitated to maintain uniform undissolved particle distribution. Within a few seconds the dispersion is sorbed on or in the tobacco fibers. Since the saturation of the tobacco fibers occurs very rapidly, it is necessary to keep them immersed for only a few seconds although longer intervals are not detrimental. It is apparent that greater or lesser concentration of adsorbed particles can be achieved by varying the material concentrations in the impregnating medium, and that this can be used as a variable process control mechanism to achieve metal oxide product variances over a wide range as desired. The desired catalytic component concentrations that can feasibly be added by this method are from 20 to 50 times greater than maximum possible concentrations that could be added by tobacco impregnation using prior processes.

The saturated tobacco fibers with high concentrations of adsorbed particles on their external surfaces are removed from the impregnating medium and placed in layers of from A to /2 inch thick in a milieu termed the photochemical reaction environment. This area is maintained at a relatively high humidity exceeding 90% to maintain the tobacco fibers at saturation moisture during the period of time the photochemical irradiation reaction takes place.

THE IRRADIATION TREATMENT Modern irradiation theories stress the necessity for free radicals, multiple energy stages, active ionized donors and the like. While the complete rationale of the present addition reaction is not completely understood, it is known that the Hill reaction provides active hydrogen and the activated cellulose undergoes cleavage and activation of the hydroxyl groups under irradiation (The Effects of Ionizing Irradiation on Natural and Synthetic High Polymers, Bovey Interscience 1958, p. 196). Such degradation of cellulose is actively shown by increase in viscosity for up to a period of 29 days in recent tests. Additionally, the active keto and aldehyde groups under irradiation of the sugars in the carrier serve as a third active site of energy excitation under irradiation. It is known that a complex is formed in which at least the metal oxide and cellulose components enter into because comparative tests indicate with and without irradiation, that only after irradiation is the iron tied up in unreactive complex form.

Products of partial photchemical degradation from the adsorbed (iron) oxide-sugar (sucrose) particles are able to react with product sites of partial photochemical degradation in the cellulose of the tobacco fibers due to the addition reaction promoting influences of the active donor radicals formed in the Hill reaction Within the tobacco fibers.

While it is possible to employ sunlight as the source of irradiation, since sunlight Will include in its broad spectrum the desired components of the visible spectrum, and an unpreferred range in the UV spectrum, however, sunlight is variable, unpredictable and extremely difficult to measure. Therefore, the results are problematical and uncertain. The present invention prefers to use two bands in the visible spectrum coinciding with the excitation frequencies for chlorophyll A and chlorophyll B necessary to make the Hill reaction go, namely, the range between 4000 and 5000 A. units and 6000 to 7000 A. units in the visible spectrum (Gen. Phys, vol. 33, p. 389) (1950). Additionally, this process requires about half as much again energy flux as visible in the ultra-violet spectrum, which broadly is below 3400 A. units and preferably in the germicidal range below 3000 A. units. Irradiation in the visible spectrum to drive the Hill reaction then, is narrowly light between 4000 and 4900 A. and between 6300 and 6800 A. Total light flux within these wave lengths per unit area of tobacco should be an optimum of /2 watt per square foot with a maximum of 1 watt per square foot and a minimum of 0.05 watt per square foot. Naturally, as with most reactions, the weaker the irradiation the longer time for reaction. A preferred light source for producing the visible light is a low pressure mercury vapor fluorescent lamp with pure scheelite as the fluorescent material and of suflicient density to obtain the required light flux. Less efiicient and non-preferred for the practice of the present invention are any continuous spectrum visible light source lamp (tungsten filament, conventional fluorescent lamp with phosphorus other than scheelite, arc lamp, etc.). Such non-preferred sources would operate at a much greater waste of electric power. The light source of ultra-violet irradiation should emit light in the germicidal ultra-violet region below 3000 A. units or preferably at 2537 A. or below, with a density sufficient to provide 4 watt per square foot of this preferred monochromatic UV line. The range for the UV flux density is from a maximum of /2 watt per square foot to a minimum of about 0.02 Watt per square foot of tobacco area. It is to be noted that the requirements for the UV energy flux are approximately one-half those for the visible light.

The range in time for application of the irradiation treatment in the present process ranges from at least about 1 hour of the highest intensity of flux density; about 10 hours of the optimum intensity of flux densities; and up to hours at the lowest intensity of flux density.

Example 1 300 grams of cut Kentucky burley at room relative humidity of 60% was placed in a dehydrating box apparatus and heated dry air was passed over and through the tobacco for a period of 10 hours until practically the moisture in the tobacco had reached equilibrium with the relative humidity of the drying medium of 15%.

Powdered iron oxide (largely Fe O with a minor proportion of lower oxide FeO) was mixed and dispersed 1:4 parts by weight in liters of sucrose solution while violent agitation stirred the mixture. Subsequently, to hydrolyze the sucrose and iron oxide to the hydrated form, the large glass container was agitated and stirred with a mechanical mixer while it was heated to boiling for approximately 20 minutes. At the end of this period the oxide sugar dispersion was diluted 1:2 Water by the addition of 20 liters of H G.

The pre-dried tobacco was placed in a tray and covered with the impregnating solution. Alternatively, the solution may be placed in the tray and the tobacco dipped or immersed in the impregnating solution. Since the impregnating step eltectively only takes a few seconds and a maximum of one minute time to achieve the adsorption of the dispersion from the tobacco fibers. The tobacco was then separated from the impregnating solution and placed in an irradiation chamber maintained in a moist atmosphere of at least 90% relative humidity. A low pressure mercury vapor fluorescent lamp (scheelite) was used as a source of visible light irradiation and the height from the target was adjusted to provide 0.5 watt per square foot energy flux and visible light irradiation was continued for 10 hours. Scheelite fluorescent delivers optimum visible irradiation in the visible spectrum in the range 6300 to 6800 A. and 4000 to 4900 A. The source of ultra-violet light in the germicidal range below 3000 A. units was provided by a commercially available low pressure mercury vapor lamp which emits ultra-violet energy in the monochromatic 2537 A. unit. The height of this lamp was adjusted to provide about half the energy flux in the visible spectrum of about Watt per square foot. Irradiation for ultra-violet light was also continued for 10 hours. At the conclusion of the irradiation procedure the tobacco was removed from the treatment chamber, moisture was suitably removed, the tobacco was vacuum cleaned and hand-rolled cigarettes were fashioned from the product.

It was noted that the tobacco product was non-staining to the hands and paper, and when tested by the standard Mine Safety Carbon Monoxide test using palladium reduction, gave consistent results showing removal of carbon monoxide on burning averaging about 80% removal. (Mine Safety Appliance Co. Monoxide Tester 08-4-7133).

Example 2A Using the prior art process of Lewton (U.S.), cigarettes there were made up for comparative testing against the cigarette produced by Example 1. The Lewton procedure of simple mixing of a ferric-ferrous oxide finely ground in range 3 to 10% by weight of tobacco was mixed with tobacco to which no special humidity procedure for dehumidifying had been practice. Comparative tests by the Standard Mine Safety Co. test showed that a moderate to good removal of carbon monoxide had been achieved on burning, averaging about 40%. However, these simple mixtures had the very undesirable visible characteristic of smearing and staining any and all physical objects with which they came into contact by the action of their externally exposed oxide pigments upon such objects.

Example 2B A 1:4 ferric oxide glucose solution diluted 1:2 aqueous by volume similar to the Example 1 procedure and forming a dispersion is impregnated on the tobacco fibers without agitation of the dispersion and without special preheating. The resulting tobacco hand-rolled into cigarettes was compared with the product of Example 1 by means of the CO Mine Safety Test. The result showed carbon monoxide removal slightly higher than the Lewton product, but somewhat below the CO removal level of the product of applicants process of Example 1, and this tobacco again showed staining properties.

Example 3 Additional comparative examples were made using a mixture of copper oxide-iron oxide wherein the iron oxide was about /3 of the total weight of the: mixture. Sample cigarettes were prepared using the procedure of applicant in Example 1, and those of the prior art in Examples 2A and 2B. The results for CO and staining were analogous to the results obtained by the pure iron oxide.

Example 4 Additional experiments were made using lactose, maltose and D-fiuctose (invert sugar) as the dispersing medium. While sucrose is preferred, these. sugars gave operable and comparable results in cigarettes.

I claim:

1. A method of treating tobacco to diminish the CO component thereof which is released during the smoking process which comprises impregnating the tobacco with between 0.5% and 8.0% by weight of the dry tobacco with a metal oxide selected from the group consisting of iron, calcium and copper oxides and hydrates and mixtures thereof, at least one-third of said metal oxide being ferric oxide, said metal oxide being disposed in the form of aqueous dispersion with a carrier selected from the group consisting of reducing sugars and carbohydrates readily hydrolyzed to reducing sugars, and selectively irradiating said impregnated tobacco with an effective amount of visible light in the range of about 4000-5000 A. and 6000-7000 A. and of UV light below about 3400 A. to form a photochemical non-staining complex of the tobacco and the metal oxide and drying, cleaning and separating said tobacco.

2. A method of claim 1, wherein the impregnated tobacco is irradiated in the visible range of about 4000- 4900 A. and 6300-6800 A. and in the UV range 3000 A.

3. A method of claim 1, wherein the amount of energy flux for irradiating visible light is in the range of about 0.05 watt per square foot hours) 1 watt per square foot (1 hour) and for irradiating UV light is in the range of about 0.02 watt per square foot (100 hours) 0.5 watt per square foot (10 hours).

4. A method according to claim 1, wherein the amount of energy flux for irradiating visible light is about 0.5 watt per square foot (10 hours) and for irradiating UV light is about 0.25 watt per square foot (10 hours).

5. A method according to claim 1, wherein said metal oxide is partially hydrated ferric oxide.

6. A method according to claim 1, wherein said aqueous dispersion of metal oxide and carrier is preheated to boiling and agitated for a period of about 5-30 minutes prior to impregnating the tobacco.

7. A method according to claim 1, wherein the tobacco is predried in an atmosphere of below about 20% relative humidity for a period of about 6-8 hours prior to impregnating the tobacco.

8. A method according to claim 1, wherein the tobacco is irradiated in a moist atmosphere wherein the relative humidity is at least 90%.

9. A non-staining irradiated tobacco produced according to claim 1.

10. A cigarette rolled from tobacco produced according to claim 1.

References Cited UNITED STATES PATENTS Re. 18,256 11/1931 Lilienfield 131-12l 2,914,072 11/1959 Tyrer et al 131-140 FOREIGN PATENTS 863,287 3/1961 Great Britain.

MELVIN D. REIN, Primary Examiner US. Cl. X.R. l31-17, 

